Two Expert — and Diverging — Views on Arctic’s Impact on Weather ‘Whiplash’

— June 19, 2013

In discussing their diverging views on impacts of rapid shrinking of Arctic sea ice, two leading scientists provide witness to the kinds of evidence-based exchanges of views not uncommon among top researchers in the climate field.

Over the past year, Jennifer Francis, Ph.D., of Rutgers University has produced compelling evidence of links between the rapid reduction in Arctic sea ice and extreme weather events in the Northern Hemisphere.

Her hypothesis — that the reduced temperature gradient between Arctic and temperate zones causes the jet stream to slow — was examined in early June’s Yale Forum“This is Not Cool” video.

The science is compelling, but — as with all scientific evidence — not yet what could be called “settled.”

For this month’s “This is Not Cool” video, independent videographer and regular Yale Forum contributor Peter Sinclair interviewed both Francis and Kevin Trenberth, Ph.D., a highly regarded senior researcher from the National Center on Atmospheric Research, NCAR, in Boulder, Co. Trenberth expresses his reservations about the jetstream/Arctic connection, and he says questions remain about whether the Arctic Ocean is a sufficiently large heat reservoir to affect hemispheric circulation patterns in the jet stream. He asks if the answer to the riddle may lie in much larger energy exchanges in the tropical oceans.

Francis and Trenberth, in their comments in this month’s video, provide insight not only into the specific issue at hand, but also into the kinds of ongoing dialogue among top scientists trying to provide evidence-based answers to some of the most complex issues posed by our changing climate.

I want to echo a comment made at SkS that’s I’d been curious about myself:

“Note how (Trenbirth) says “there might be influence somewhere in Europe, for example, but not over entire NH”. To which I may reply: well, the same jetstream flies over Canada US and in Europe, why do you think America is “immune” to it?

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And sorry for doing this,
but it is only slightly off topic
considering how science skeptics love pointing out the 1920/30s arctic warming (where they fail to mention the warming was rather localized, originating around Spitsbergen) trying to imply that there is nothing unusual about current events.

Which has introduced me to the notion that intense navel activity caused a great deal of ocean mixing, disrupting the thermohaline current, and leading to the freak warming event that started off Spitsbergen and spread outward from there:

” a long barrage between the Orkney Islands and Norway … (USA and UK mines laid) 73.000 mines __about 5,000 exploded prematurely soon after laying __20,000 mines were disposed of while the work was in progress __from the remaining ca. 50,000 mines __more than 30,000 mines were already ‘gone’ in spring 1919, either drifted away, or exploded during winter storms; __rest 20,000 were swept in 1919.” {ch.8 p.94}

In all something like 200,000 mines were laid in various North Atlantic locations.

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As for ships and U-boats:

“The situation became dramatic when U-boats destroyed more ships than Britain could build in early 1917. In April 1917, the same total rate of the previous annual rate of 1916, ca. 850,000 tons, was destroyed by U-boats. In April 1917, Britain together with the Allies lost 10 vessels every day. During the year of 1917, U-boats alone sank 6,200,000 tons, which means more than 3000 ships, and, during the war months of 1918, another 2,500,000 ship tonnage. The total loss of the Allies ship tonnage during WWI is of about 12,000,000 tons, namely 5,200 vessels. The total loss of the Allies together with the Axis naval vessels (battle ships, cruisers, destroyers, sub-marines, and other naval ships) amounted to 650, respectively 1,200,000 tons.” {ch.8 p.88}

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It’s one of those thoughts that at first blush is way out there, but then on reflection and considering the new found appreciation for the deep ocean churning whales and other sea creatures produce as they dive to deep depths then return to surface (http://www.biogeosciences-discuss.net/9/8387/2012/bgd-9-8387-2012.html) –
it doesn’t seem so far fetched.

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I’m curious how has the scientific community reacted to Bernaerts’ hypothesis?

The mechanism linking Arctic amplification (AA: increased sensitivity of the Arctic to global warming or cooling) to changes in the jet stream that Steve Vavrus and I proposed and demonstrated in our March 2012 paper involves more than just sea-ice loss. While the ice loss is the largest contributor to AA in fall and early winter, rapid Arctic warming is also driven by the pronounced negative trend in snow cover on high-latitude land in spring and early summer, and even more strongly by the increase in water vapor at high latitudes, which affects AA in all months. That water vapor warms the Arctic in all seasons in 3 ways: it is a greenhouse gas, it releases latent heat into the atmosphere when it condenses into clouds, and those additional clouds also trap heat below them. Most of the modeling studies to date that examine the Arctic’s effects on the large-scale atmospheric circulation have focused only on the influence of sea-ice loss. I believe this is the reason that most of those studies fail to find a robust response, while the real world (which DOES include all the contributions to AA) is responding more strongly. It is also important to note that AA has emerged from the noise of natural variability only in the last decade or two (challenging tests of statistical significance), it is strongest in the fall and near the surface (because of sea-ice loss), and it is becoming evident in all seasons and through a deep atmospheric layer (because of increased water vapor). This must inevitably have a more pronounced effect on the polar jet stream as we continue to warm the planet by burning fossil fuels.